Transporting hydrocarbon mixtures as a slurry

ABSTRACT

HYDROCARBON MIXTURES (E.G. CRUDE OIL) HAVING AN AVERGE POUR POINT ABOVE THE AVERAGE MINIMUM TEMPERATURE OF A TRANSPORTING SYSTEM ARE EFFECTIVELY TRANSPORTED BY FIRST FRACTIONATING THE MIXTURE INTO AT LEAST A RELATIVELY HIGH POUR POINT FRACTION AND A RELATIVELY LOW POUR POINT FRACTION, CONGEALING THE HIGH POUR FRACTION, E.G. BY PRILLING, DISPERSING INTO A WATER BATH, ETC., AND THEREAFTER SLYRRYING AT LEAST A PORTION OF THE CONGEALED FRACTION WITH THE LOW POUR POINT FRACTION AND TRANSPORTING THE SLURRY, PREFERABLY IN A CONDUIT, AT A TEMPERATURE BELOW ABOUT THE CONGEALATION TEMPERATURE OF THE CONGEALED FRACTION. FRACTIONATION IS PREFERABLY EFFECTED BY DISTILLATION. DILUENTS E.G. LOW POUR POINT HYDROCARBONS SUCH AS RESEVOIR CONDENSATES, CAN BE ADMIXED WITH THE SLURRY TO IMPROVE THE PUMPABILITY THEREOF. ALSO, A PORTION, E.G. UP TO 50% BY VOLUME, OF THE OTHERWISE HIGH POUR POINT FRACTION CAN BE CRACKED DURING FRACTIONATION TO IMPROVE THE FLUIDITY IF THE SLURRY.

TRANSPORTING HYDROCARBON MIXTURES AS A SLURRY La Vaun S. Merrill, Jr., Englewood, and Dennis E. Drnyer, William B. Gogarty, and George A. Pouska, Littleton, Colo., assignors to Marathon Oil Company,

Findlay, Ohio No. Drawing. Filed Sept. 18, 1972, Ser. No. 290,205

. Int. Cl. Clog 43/02 U.S. Cl. 208-370 38 Claims ABSTRACT on THE orscLosuR Hydrocarbon mixtures (e.g. crude oil) having an averthe low pour point fraction and transporting the slurry,

preferably in a conduit, at a temperature below about the congelation temperature of the congealed fraction. Frac tionntion is preferably effected by distillation. Diluents, e.g. low pour point hydrocarbons such as reservoir condensates, can be admixed with the slurry to improve the polyphosphates can be added to increase the waters ability to selectively adhere to the steel pipe and to displace any oil from the surface of the pipe without forming an emulsion. I

Scott et al. in U.S. 3,269,40lteaches facilitating flow of wax-bearing oil in a pipeline by dissolving in the oil, at superatmospheric pressure and while above its pour point, agas, B-gi N 00 flue gas, and hydrocarbons containing less than 3 carbon atoms. The gas becomes associated in some way with the wax crystals and prevents the precipitated wax from agglomerating to form strong wax structures." Also, the gas collects on the surfaces of the wax particles-especially the larger ones-to form films of gas envelopes which isolate the particles from one another and prevents the wax particles from combining.

solvent liquid (cg. water), maintained at a temperature above the solidification temperature of the wax'and thereafter cooling the dispersion to solidify the dispersed droplets into discrete solid particles. The particles can be pumpability thereof. Also, aportion, e.g. up to 50% by carbon mixtures. The hydrocarbon, e.g. crude oil, isfirst fractionated into at least two fractions, one fraction is congealed into spherical particles and then slurried with the other fraction'and the slurry transported preferably in a conduit.

- Description of the prior art Pumping of viscous crude oils at temperatures below the pour point thereof is very diiiicult. Heattransfer methods and chemical agents to improve fluid flow properties have been studied. Pour point depressers have been tried as well as diluents to improve the pumpability. Visbreaking agents have also been tried but with little success. In addition, the oilhas been congealed, suspended in water and the combination pumped at temperatures below the pour point of the crude oil.

Examples of patents which represent the art include:

Kells in U.S. 271,080 separates wax from crude oils by pumping the crude oil, egg. in small streams or jets, into the bottom of a tank containing a brine at a temperature sufiiciently low to congeal the'wax. The congealed wax is recovered in the brine.

Persch in U.S. 1,154,485 blasts air under-pressure into crude oil to form an emulsion of air and oil to increase the fluidity of the oil.

Oberfell et al. in U.S. 2,526,966 teaches transporting viscous crude oils by removing the light hydrocarbons (including straight-run gasoline), hydrogenating the residue to increase the fluidity thereof and then combining the hydrogenated product and'the light hydrocarbons and pumping the mixture. 1

Chilton et al. in U.S. 2,821,205 forms a film of water on the interior wall of the pipe to improve the pumpability of viscous oil. In addition,.a light-petroleum or condensed casing-head gas can be mixed with the crude 'oil toreduce the viscosity. Agcnts such as phosphatesand above the scasonably ambient temperature of the transcoated with finely divided coating solids such as calcium' carbonate, etc. Watanabe teaches that it is known in the artto' disperse waxy particles by molding, prilling, spray drying,v extruding, etc. i Titus in US. 3,527,692 transports crushed oil shale in a solvent slurry Tltenoil shale is first comminuted to a size of -325 meshand .then suspended in a solvent such as crude oil, retorted shale oil, or a fraction thereof.

I Allen in U.S. 3,548,846 teaches transporting waxy crude oils by incorporating propane or butane with the crude oil.

.Vairogs in US. 3,618,624 transports viscous crude oils by incorporating a miscible gas, e.g. CO methane, ethane, etc. into the crude to reduce the viscosity of the viscous crude I l The art has also usedtracer lines and large heat exchangers placed intermittently along the pipeline to maintain the crude oil above its pour point and thus facilitate ;pumping of same. The main disadvantage of these metlr ods is the crude oil tends to set up? during shutdowns. This technology, except for'heat transfer systems and crude oil-water suspension systcrns,,has generally proven to be economically unattractive from a commercial standpoint. I

SUMMARYOF THE INVENTION Applicants have discovered a commercially attractive process oftransporting viscous hydrocarbon mixtures by first fractionatingjthe hydroc'arbonmixture into at least two fractions, one fraction having a relatively high pour point and the other fraction having a relatively low pour PREFERRED EMBODIMENTS. OF THE INVENTION Hydrocarbon mixtures' 'having average pour points portation system, e.g., a pipeline, are particularly applijcable with this invention. Examples of hydrocarbon mixtures include crude oil,"shale oil, tar sandoil, fuel oil,

5 gas oil, like hydrocarbon mixtures and mixtures of two per second-) and preferably'below 10 ft./sec.g and more tures. Crude oils are particularly useful with'this invention and especially those classified as waxy" crude oils.

Examples of the latter include crude oils which exhibit a waxy gell appearance at seasonably ambient temperature and which contain'about 1% to about 80% wax 5 (wax is defined as the precipitate which forms after one point above the average minimum temperature'of the.

transporting system, e.g. a pipeline. Examples of average pour points of crude oils particularly useful with this invention include about -10 to about 200 F. and prefer ably about 0' to about 150 F. l

The hydrocarbon mixture is first fractionated into at least two fractions, an overheads fraction which has a relatively low pour point (also identified as having a density and viscosity at a given temperature lower than the original hydrocarbon mixture) and a bottoms fraction which has a relatively high pour point (also identified as having a density and viscosity at a given temperature above that of the original hydrocarbon mixture). The. bottoms fraction can be any portion of the original hydrocarbon r'nixture; e.g., it can be about 1 to about 80% and preferably about 20 to about 70% and more,

preferably about to about 60% by weight of the original hydrocarbon mixture. It is to be understood that fractions other than the overheads and bottom fractions can be obtained and these fractions used in other processing streams. v I 2 'Fractionation can be accomplished at atmospheric pressure, sub or superatmospheric pressure and atlow and high temperatures by processes such as distillation,

solvent extraction, membrane fractionation, crystallization, or any process which separates the hydrocarbon mixture into at least two fractions. Optionally, up to preferably up to 42% and more preferably up to 33% by volume of the equivalent high pour point'frac tion can be cracked (by thermal, hydrogenation, catalytical or combinations thereof) during fractionationxor before'congelation.

The low pour point fraction should have a pour point at least 1. and preferably at least about 5 F. below the average of the minimum temperature range ofjthle transporting system, e.g. a pipeline or a combinationof. pipe- '45 line and tank battery.

stantially solid particles having an average diameter of. about 0.05 to about 20 or more mm. (millimeters) and, preferably about 0.1 to about 5 mm. and more preferably about 0.5 to about 3 mm. The particles are preferably spherical and can be of substantially. uniform or random diameter sizes. Comminution is'accornplished by prilling, extruding, molding, shredding, grinding, andlike methods for dispersing or disintegrating the uncongealed or congealed material. Where-shredding or grinding is used, 'comminution preferably takes place .after-congelation. Congealing as used herein includes solidification,

crystallization, making into a consistency like jelly, etc.

The high pour point fraction is preferably about'l to about 150 and more preferably about 10 to about 100 F. above its average con'gelation temperature as it'enters the congelation and comminution steps. Prilling can be accomplished by spraying the bottoms fraction, into a prilling tower where the prill comes in contact with gas (e.g.'air, N CO naturalgas, or like gases) and/or water. Optionally, "theprill is collected in a water bath at the bottom of the tower. Air is the preferred gas and is preferably moved through'the prilling tower, bynatural or forced convection, at velocities sufficient to not exceed the drop or settling rate. of the prill falling throughthe prilling tower; air velocities below about 20 fa /sec. (feet 7 preferably belowabout 5 ft./sec. are useful. Temperature of the air, entering the prilling tower is preferably aboutl to about 230 and more preferably about 10 to about 150 below the congealing temperature of the prill. Temperature of theair leaving the prilling tower .is preferably about 230. below to about 150 above and more preferablyabout below to about 10F. above .the average congealing temperature of the high pour point fraction entering the, prilling tower. Water is pref erably sprayed into the tower alongwith the air, the

water being ata temperature at least about 5 F. and

preferably at least about 20 F. below the congealing temperature of the high pour point fraction. Also, it is preferred that; the water be sprayed into the tower in a direction normal to the airflow direction.

Another method for dispersing the high pour point fraction isby extruding or spraying into water, the fraction preferablyat about 5 to about 100 F. and more preferably isv about to about 220? F. above its average 'congelation temperature. The water preferably flows countercurrent to the movement of the introduced high pour point fraction and more preferably the water is in'turbulent flow at the injection point of the high pour point fraction. The dispersed high pour pointfraction is lthereafter congealed, by admixing cooler water, e.g. at

transported.

A surfactant can be incorporated into the high pour point fraction: before it is congealed, e.g'. it can be ad- 'mixed withthe fraction before or as it enters the prilling tower. Volume amountsof about 0.0001 to about 20% and preferably about 0.001 to about 10%, and more preferably about 0.01 to about 1% by volume, based on the fraction, are useful. The surfactant should have sulficieut oleophilic property to solubilize into or act like it is miscible with the fraction. It is postulated that the surfactant molecules tend to orient their hydrophilic portion radially at thedroplet surface, Theoretically, this ghappensas the droplets of'wax are formed, imparting a more hydrophilic property to the droplet. Examples of useful surfactants include fatty acids (e.g. those con- '='taining about 10 to about 20 carbon atoms) and prefer- 'ab ly monovalent cationcontaining salts thereof. Sorbitan monolaurateis an example of a useful surfactant.-Preferably the surfactant is a petroleum sulfonate preferably having a monovalent cation, e.g.' Na+, and preferably having an-average equivalent weight of about 200 to about 600 and more preferably about 250 to about 500 and most preferably about 350to' about 420.

After thehigh pour point fraction is congealed into the desired particle size,-at least'a'portion and preferably all y of the particlesare vslurried (e.'g. combined or l mixed) with the-low pour point fraction. The concentration of congealed fraction inthe slurry is-preferably about 1% to about 80% and more preferably about 5% to about 55% and most preferably abou t"10% to about 50% by weightDuri-ng the slurrying operation, the temperature I of the low pour point fraction isap'referably about 30 below ,to' about 30,above'an'd more preferablyabout 20 below to about 20 above the minimum, seasonably ambient temperature of the transportation system. Also, the

. temperatureof thelow pour point fraction during slurrying should be below and preferably at,least about 5 F.

andv more preferably at least about' 15 F. and most pref. erably at-least about 30 F. below the solution temper- 'ature of the congealed high pour point fraction. A liquid diluent, such as straight] run gasoline, reservoir condensate,'-or like hydrocarbon, can be admixed with the low pour point fraction either before or after the: slurrying operation-any diluent which is miscible with the low pour pointfraction'and which preferably. has a pour ticles can be coatedwith a solid material. Such inhibits agglomeration of the particles and may permit higher slurry temperatures during transportation. Examples of coatings include those disclosed in US. 3,468,986 to Watanabe. Where the high pour point fraction is prilled, the coating can be applied as a spray, either hydrous or anhydrous, or as an aqueous bath containing the solidmaterial. Examples of useful coating materials include inorganic and organic salts of the metals of Group II, III, IV-A, V, VI, VII, and VIII of the Periodic Table;

synthetic resins such as cellulose acetate, polystyrene, polyethylene, polyvinyl acetate, and like resins; and other materials such as clay (e.g. bentonlte), kaolin, Fuller's earth 0.014 inch circularnozzle at a rate of about 0.3 gallon/ hour. Nozzle temperature is maintained at 118 F.-127 F. As' the liquid leaves the nozzle, it solidified into beads upon contact with the air. Average diameter size of the beads is about 0.1-1 mm. The beads fall about 7.5 feet into the overheadstraction, the resulting slurry is maintained at about 32 F.

The slurry is pumped through feet of as" p pe in series with 8' of A" tubing at a rate of about 3.7-8.0 g.p.m. (gallons per minute). During pumping, the term pcrature never exceeds 74 F. t v

After pumping, the slurry is examined and it appears the beads are not substantially sheared and are not in solution with the overheads fraction.

EXAMPLE II overheads temperature of 500 F. at the end point and and other aluminum silicates, limestone, etc. Calcium carbonnie is a preferred coating material.

A gas miscible with the low pour point fraction but preferably immiscible with the congealed fraction can be admixed with the slurry to reduce the viscosity thereof.

The gas may be liquid at the temperature and pressure of the transportation system. Examples of such miscible gases include CO lower hydrocarbons containing less than 4 carbon atoms, etc. Also, the miscible gas can be injected into the slurry under conditions such that the gas is present in concentrations greater than that at atmospheric conditions. Preferably, the mixture is saturated with CO, at superatmospheric pressures.

The slurry can be transported in bulk, e.g. tank car, tank truck, tank trailer, tank, barge, tanker or like means, but is preferably transported in a conduit, such as a pipeline. or course, the conduit or pipeline system will have tank batteries, i.e. collection or holding tanks, associated with it.

The slurry can be transported under laminar, transitional (e.g. ReyncldsNumber range of about 2000 to about 4000) or turbulent flow conditions inthe conduit.

Turbulent flow conditions may be preferred where it is desired to maintain thecongealed particlesin a homogeneous dispersed state. 1

The slurry is preferably transported in a conduit wherein the average msximum'temperature of the conduit in at least its major initial length is below the solution temperature of the congealed fraction. The average maximum temperature oi the conduit is preferably at least about 1 F. below and more'preferably at least about, 5F. below the average solution temperature of the congealed fraction within the slurry-solution temperature as used herein means the temperature at which substantially all of the congealed particles are in solution within the continuous phase of the slurry. In addition, the average temperatu're of the conduit should not be below the average pour point of the low pour point fraction and preferably is at least about 1 F. and more preferably at least about 5 F. above this pour point- Working examples:

EXAMPLE I A waxy crude oil from the Altamont Field in Utahsv Uinta Basin has an average API gravity of about 40? and has an average pour point of about 110 F. This crude tion). The final overheads temperature on the distillation column is 266 F. and the final temperature of the bottoms fraction (i.e. high pour point fraction) is 581 F. Pour point of the bottoms fraction is 118 F. The bottoms fraction is prilled by sprayingit at a temperature of 160 F. into the atmosphere (air at 80 F.) through a a bottoms temperature of about 700 F. at the end point.

Pressure of the distlllationcolumn is about 632 mm. rig

ab. Thebottoms fraction is separated and sent to a prilhng tower. The bottoms traction (average pour point==128 F.) is sprayed at 180 F. into a prilling tower. Average V 80% by'weig ht. .oil is distilled such that 32% by weight ofthe crude is taken as an overheads fraction (i.e.-low pour point fractemperature of air entering the tower is about F. and the average temperature of air leaving is about F.-- average velocity otthe air is about 2 rib/sec. About 200 gab/hr. of water is sprayed (atomized) into the, lower section of the tower to facilitate congelation of the pull. The prill tells about 27 feet to the bottom of the prilling tower where it is collected in water maintained at 60-6$ F. The average diameter size of the prill is about 0.8- 1.25 mm.

The aqueous suspension of the prill is separated into water and the prill. Thereafter, the prill is slurried with the overheads fraction at about 40 F. The slurry is transported in a pipeline at. temperatures not exceeding 75 F.

, under laminar and transitional flow conditions. It is ob-.

served that the slurry acts as a Bingham plastic.

' EXAMPLE in I y The procedure of Example 11 is repeated except the bottoms fraction is prilled into an aqueous bath containing about 1% by weight of calcium carbonateTlhe-calcium carbonate coats the prill with at least a mono-melee What is claimedis: I .l p

1. A processfor transporting a hydrocarbon mixture as a slurry,- the process comprising fractionating the hydrocarbon mixture into at least a relatively low pour point fraction and a relatively high p'our pointf fraction, substantially congealing at least a portion of the relatively high pour point fraction to obtain congealed particles and thereafter slurryin'g the congealed particlesin the relatively low pour point fraction at a temperature below about the solution temperature or the congealed particles in the low pour point fraction-and transporting the slurry vin the transportation system.

2. The process of claiml wherein the hydrocarbon mixture is a. waxy" crudeoil. a

3.- The process of claim Z-Wherein the waxy crude oil has. an average wax concentration of about 1 to about 4.:The process'of claim 2 wherein the waxy crude oil has an average pour point above theIaverage seasonably minimum temperature of thetransportation system.

5. Th e process of claim 1 wherein ,the'hydrocarb'on inixtureis a crude oil having an average pour point of about -l0 to about 200. F.

system is a conduit.

6. The process of claim 1 wherein the transportation t 16. The process of claim-15 wherein v 8. The process of claim 6 wherein the slurry is trans- 10. The process of claim 1 wherein slurrying is effected ata temperature at least about 5' F. below the average solution temperature of the congealed particles in the relatively low pour point fractio 11. The process of claim 1 wherein the relatively high pour point fraction is congealed at a temperature at'least about 5 F. below its pour point. a v

, 12. The process of claim 1 wherein congelation is effected by prilling.

13. The process weight of the equivalent amount the high pour point fraction is cracked before it is congealed.

14. The process of claim 1. wherein the average diarn= agar oi the congealed particles is about 0.05 to about mm. 15. A process at transporting in a conduit a "waxy" crude oil as a slurry, the process comprising:

(l) tractionating the crude oil into at least a relatively low pour point fraction and a relatively high pour point fraction, the relatively high pour oint traction equivalent to about ito about 80% y weight of the original weight of the crude oil, (2) substantially congeaiing at least a portion of the relatively high pour point-traction to obtaind congealed particles, a (3) thereafter slurrying the congealed particles with the relatively low pour point fraction at a temperature below about the solution temperature of the congealed particles in the low pour point fraction, and (4) transporting the slurry in a conduit at a temperas ture below about the solution temperature oi. the congealed particles in at least a major, initial length oftheconduitp the concentration of the congealed particles in the slurry is about 5 to about 55% by weight.

17. The process ofclaim 15 wherein the average pour I point of the crude oil is between about to about 200 F. I

effected by distillation andwherein'at least a portion of the crude oil is cracked during the distillation.

22. The process of claim wherein an oleophilic surof claim 1 wherein up to 50% by' claim 15 wherein up to about J a e factant is admixed with the high pour point fraction before it is congealed.

23. The process of claim 22 wherein about 0.0001 to about 20% by volume, based on the high pour point fraction, of the surfactant is admixed.

24. The process of claim 15 wherein a gas miscible with the low pour point fraction is admixed with the slurry.

25. The process of claim 24 wherein the gas is CO 26. The process of claim 15 wherein adrag reducing agent is admixed with the slurry. I p

27. The process of claim 15 wherein a liquid diluent is admixed with the low pour point fraction either before or after sl'urrying.

28. The process or claim 15 wherein the average digtgreter of the congealed particles is about 0.05 to about 29. The process of claim 15 wherein the congealed particles are substantially coated with a solid material.

30. The process at claim 29 wherein the solid material is an inorganic salt or an organic salt of the metals of Group II. II-LIV-A, V, VI, VII, and VIII of the Periodic Table. i

31. The recess oi claim 15 wherein the average diameter at e congealed particles is about 0.1 to about 5 32. The process oi claim 15 wherein the congealed particles are. substantially coated with calcium carbonate. The process of. elaiml a wherein the concentra tion at the congealed particlesin the slurry is about 10% to about by weight;

34. The process at claim 15 wherein the slurry is transported under substantially laminar flow condition.

35. The process of claintll wherein the slurry is transported under substantially transitional flowcondltion.

36. The processotcl'alm 15 wherein the sin is trans ported under substantially turbulent flow condit on.

37. The process of claim 15 wherein the average congealed particle is substantially spherical. I 1

,38. The process of claim 1! wherein the average diameter of the congealed particles is about 0.1 tov about 5 mm. and wherein the average congealed particle is substantially spherical vinshapo.

References Cited g UNITED STATES PATENTS Bake-s -t zen-as 2,726,990 12/ 1955 3,234,122 2/1966 Aliibone et a1. "3208-370 3,294,672 12/1966 --Torobin .208'-33 us. 01.. X.R. 

